There have been various body compressing devices proposed to sequentially squeeze a patient's limbs, usually the legs, to aid in blood circulation. Such compression devices are intended to prevent pooling of blood in limb extremities where a deep vein thrombosis (blood clot) can form.
One type of patient limb compression device is described in a co-pending application by Bishop and Choksi, entitled Pulsatile Stocking and Bladder Therefor, Ser. No. 820,104, filed July 29, 1977, now U.S. Pat. No. 4,153,050. The subject matter of the present application deals with an improved pumping system for sequentially inflating a limb compressing device, such as the stocking described in the above co-pending application.
It has been known to use air compressors, and tanks of compressed air to inflate body compressing devices, which were thereafter deflated by venting a valve to the atmosphere. Examples of such inflation systems are described in U.S. Pat. Nos. 2,140,898; 2,145,932; 2,674,231; 3,901,221; and 3,942,518. The inflation systems described in this prior art would either provide a very slow rise time to the desired pressure, or include large cumbersome compressed air tanks or compressors that are not easily portable throughout the hospital. It is noted that the compact air supply unit described in the present application may be conveniently disconnected from the stocking described in the above copending Bishop and Choksi application. The stocking/bladder device is lightweight and pliable permitting ambulatory patients to walk while still wearing such stockings.
It has also been determined that blood circulation is improved if the compression device is quickly inflated to a slight pressure peak, 5 to 10 mm Hg above its desired plateau pressure, and held at a generally constant plateau pressure for more than 10 seconds, and then deflated. The prior inflation systems for limb compressing devices inflated them in either one or two steps to a peak pressure point and immediately deflated the device. With such arrangement, much of the blood flow stimulation occurs at less than peak pressure. It is believed that a greater volume of blood can be pumped through the limb with a compression cycle that has a generally constant plateau pressure for a considerable period of time.